Contact layout structure

ABSTRACT

A contact layout structure includes a substrate having at least a first region defined thereon, plural sets of first contact layouts positioned along a predetermined direction in the first region, and a plurality of second contact layouts positioned in the first region. Each set of the first contact layouts further comprises two square contact units and two adjacent rectangle contact units positioned in between the two square contact units. Each of the rectangle contact units comprises two opposite long sides and two opposite short sides, and a length of the long sides is not equal to the a length of the short sides.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.12/122,733, filed May 19, 2008, which is included in its entirety hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a contact layout structure, and moreparticularly, to a contact layout structure positioned in a denseregion.

2. Description of the Prior Art

Photolithography process has been an essential process in semiconductormanufacturing procedures. It includes steps of providing a photomask orphotomasks having designed patterns such as circuit patterns, dopedregion patterns, or contact layout patterns and transferring saidpatterns to a photoresist formed on a substrate by an exposure step anda development step, thus those complicated patterns are obtained on thesemiconductor chips precisely. After the photolithography process,implantations or etching processes are performed to construct thoseintricate circuit structures.

With a trend toward miniaturization of the semiconductor industry, andimprovement in semiconductor manufacturing process, it is capable offorming both dense regions and iso regions on one chip. However, it iswell-known that critical dimension (CD) of a layout pattern such as acontact layout pattern always faces an optical limit. In particular, anundesired condition that the opening merged in the dense regions isoften found in after-development-inspection (ADI).

In addition, please refer to FIG. 1, which is a cross-sectional view ofa conventional share contact opening. As shown in FIG. 1, a sharecontact opening 110 is positioned in a dense region such as a staticrandom access memory (SRAM) region 102 of a substrate 100. The substrate100 further includes a plurality of shallow trench isolations (STIs) 104used to provide electrical isolation. The share contact opening 110 isformed in a dielectric layer 140 for forming a share contact (not shown)in following process. The share contact is used to electrically connecta source/drain 124, which is on an active region, of a transistor 120and a gate 132 of another transistor 130, which is also formed on theactive region, to an upper circuit layer. As shown in FIG. 1, becausethe share contact connects source/drain 124 and gate 132 of differenttransistor 120, 130, the share contact opening 110 is often made largerthan conventional contact opening 112.

It is noteworthy that in the etching process used to form the contactopening, micro-loading effect caused by density difference between thedense region and the iso region often makes etch ratio in the denseregion lower than that in the iso region. Furthermore, another problemis found in the dense region: because the share contact opening 110 islarger than the other contact opening 112, it is found that, in the sameetching process, the conventional contact opening 112 has not beencompletely formed while the share contact opening 110 is well formed. Inother words, when the conventional contact opening 112 is completelyformed, the share contact opening 110 will be over-etched, even causingdamage to the underneath transistor or the active region and thusadversely influences the yield. Those skilled in the art will easilyconclude that although the share contact increases the utility rate ofthe valuable chip area, it simultaneously raises difficulty orcomplexity of the etching process control.

Therefore, a contact layout structure is needed to fundamentally avoidopenings from the merging problem found in ADI and to avoid problemshappening to process control as mentioned above.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the claimed invention to providea contact layout structure capable of avoiding openings merging found inADI and simplifying etching process control.

According to the claimed invention, a contact layout structure isprovided. The contact layout structure comprises a substrate having atleast a first region defined thereon, plural sets of first contactlayouts positioned along a predetermined direction in the first region,and a plurality of second contact layouts positioned in the firstregion. Each set of the first contact layouts further comprises twosquare contact units and two adjacent rectangle contact units positionedin between the two square contact units. Each of the rectangle contactunits comprises two opposite long sides and two opposite short sides,and a length of the long sides is not equal to the a length of the shortsides.

According to the claimed invention, a contact structure is provided. Thecontact structure comprises a substrate having at least a first regiondefined thereon and plural sets of first contacts positioned along apredetermined direction in the first region. Each set of the firstcontacts comprises two first contact units and two adjacent secondcontact units positioned in between the two first contact units. Aconnection line of center points of the second contact units is notoverlapped to a connection line of center points of the first contactunits.

According to the contact layout structure and the contact structureprovided by the present invention, the two adjacent rectangle contactunits that are positioned in between the two square contact units or onthe gate line regions are rendered to obtain more valuable spaces in thedense region, and to avoid the merging problem happening between therectangle contact unit and the square contact unit found in ADI.Furthermore, one rectangle contact unit and one adjacent square contactunit are able to replace a conventional share contact to avoid thedilemmatic problem of obtainment of either incomplete conventionalcontact openings or forming over-etched share contact openings in onesame etching process.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conventional share contactopening.

FIGS. 2 and 3 are schematic drawings of a contact layout structureprovided by a preferred embodiment of the present invention.

FIG. 4 is a SEM photograph of a contact opening pattern formed by thecontact layout structure provided by the present invention.

DETAILED DESCRIPTION

Please refer to FIGS. 2 and 3, which are schematic drawings of a contactlayout structure provided by a preferred embodiment of the presentinvention. As shown in FIG. 2, a substrate 200 having at least a firstregion 202 is provided. The first region 202 can be a dense region, forexample, the first region 202 is a static random access memory (SRAM)region. The substrate 200 further comprises at least a second region(not shown), which comprises iso region.

Please refer to FIG. 2 again. The contact layout structure provided bythe preferred embodiment further comprises plural sets of first contactlayout 210 positioned along a predetermined direction in the firstregion 200. The predetermined direction is a Y-axis direction in thepresent preferred embodiment. However, it is not limited to this, andthe predetermined direction can be an X-axis direction in othermodifications of the present embodiment. Each set of the first contactlayouts 210 comprises two square contact units 212 and two adjacentrectangle contact units 214 positioned in between the two square contactunits 212. A width-to-length ratio of the rectangle contact unit 214 isbetween 1:1.8 and 1:1.2. An area ratio of the rectangle contact unit 214to the square contact unit 212 is between 1:0.8 and 1:1.2. It isnoteworthy that the two rectangle contact units 214 are adjacent withits long sides and the long sides of the rectangle contact units 214 areparallel with each other. And the long sides of the rectangle contactunit 214 are perpendicular to the predetermined direction.

Additionally, a connection line 220 of center points of the two squarecontact units 212 is parallel with a connection line 222 of centerpoints of the two rectangle contact units 214 as shown in FIG. 2. In amodification of the present preferred embodiment, the connection line222 of the center points of the two rectangle contact units 214 overlapsthe connection line 220 of the center points of the two square contactunits 212, as shown in FIG. 3.

In the present preferred embodiment, the contact layout structurefurther comprises a plurality of second contact layouts 250 positionedin the first region 202. The second contact layouts 250 respectivelyhave a square contact unit.

Please refer to FIG. 4, which is a SEM photograph of a contact openingpattern formed by the contact layout structure provided by the presentinvention. It is noteworthy that, in an exposure step used to transferthe contact layouts, both square and rectangle layout units aretransformed into round shapes due to the main lope and the side lope ofdifferent intensity distributions of the incident light. Thus theobtained contact openings are all in round shapes, as shown in FIG. 4.

The contact layout structure provided by the present preferredembodiment is more preferable to dense regions of a chip. Since a greatamount of contacts are to be formed in the limited dense region, thecontact layout structure provides two adjacent rectangle contact units214 that are positioned between the two square contact units 212 toobtain more valuable spaces in the dense region of a chip. Furthermore,to prevent contact openings from merging problem found in ADI, therectangle contact units 214 are positioned with its long sideperpendicular to the predetermined direction, therefore a spacingbetween the rectangle contact unit 214 and its adjacent square contactunit 212 is larger than a spacing between the square contact units ifthe first contact layout 210 comprises all square contact units.Accordingly, openings merging of the rectangle contact unit 214 and thesquare contact unit 212 found in ADI is avoided.

Please refer to FIGS. 2 and 4 again, which illustrate another preferredembodiment of the present invention. According to the preferredembodiment, the first region 202 further comprises a plurality of activeregions 204 and a plurality of gate line regions 206 respectivelycorresponding to active regions and gate line regions of a chip. Asshown in FIG. 2, the contact layout structure provided by the preferredembodiment comprises a plurality of square contact units 212/250respectively positioned in the active region 204 of the first region 202and a plurality of rectangle contact units 214 respectively positionedin the gate line region 206 of the first region 202. The long sides ofthe rectangle contact units 214 are parallel with an extending directionof the gate line region 206. Furthermore, the rectangle contact units214 are arranged by twos, and long sides of the adjacent rectanglecontact units 214 are parallel with each other. As mentioned above, awidth-to-length ratio of the rectangle contact unit 214 is between 1:1.8and 1:1.2. And an area ratio of the rectangle contact unit 214 to thesquare contact unit 212/250 is between 1:0.8 and 1:1.2.

According to the contact layout structure provided by the preferredembodiment, the rectangle contact units 214 are positioned in the gateline regions 206 with its long side parallel with the extendingdirection of the gate line region 206. Compared with the conventionalcontact layout that the both gate line regions 206 and the active region204 are provided with square contact units, the contact layout structureprovided by the preferred embodiment obtains larger spacing between therectangle contact unit 214 and its adjacent square contact unit 212,thus opening merging problems found in ADI are avoided. Furthermore,since one rectangle contact unit 214 and its adjacent square contactunit 212, which possess substantially equal areas, are able to replace aconventional share contact layout, the openings formed in followingetching process are more comparable. Therefore difficulty inconventional etching process control that is when the share contactopenings are well formed, the conventional contact openings have notbeen completely formed, or when the conventional contact openings arecompletely, the share contact openings are already over-etched, isavoided.

In summary, the contact layout structure provided by the presentinvention renders the two adjacent rectangle contact units that arepositioned in between the two square contact units or on the gate lineregion to obtain more valuable spaces in the dense region, and to avoidthe merging problem happening between the rectangle contact units andthe square contact unit found in ADI. Furthermore, one rectangle contactunit and its adjacent square contact unit are used to replace aconventional share contact layout to avoid the dilemmatic problem ofobtainment of either incomplete conventional contact openings or formingover-etched share contact openings in the same etching process.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A contact layout structure comprising: a substrate having at least afirst region defined thereon; plural sets of first contact layoutspositioned along a predetermined direction in the first region, each setof the first contact layouts comprises: two square contact units; andtwo adjacent rectangle contact units positioned in between the twosquare contact units, each of the rectangle contact units comprising twoopposite long sides and two opposite short sides, and a length of thelong sides being not equal to the a length of the short sides; and aplurality of second contact layouts positioned in the first region. 2.The contact layout structure of claim 1, wherein the first regioncomprises a dense region.
 3. The contact layout structure of claim 2,wherein the first region comprises a static random access memory (SRAM)region.
 4. The contact layout structure of claim 1, wherein thepredetermined direction is an X-axis direction or a Y-axis direction. 5.The contact layout structure of claim 1, wherein a connection line ofcenter points of the two square contact units is parallel with aconnection line of center points of the two rectangle contact units. 6.The contact layout structure of claim 5, wherein the connection line ofthe center points of the two square contact units overlaps theconnection line of the center points of the two rectangle contact units.7. The contact layout structure of claim 1, wherein the long sides ofeach rectangle contact unit is perpendicular to the predetermineddirection.
 8. The contact layout structure of claim 1, wherein a longside-to-short side ratio of the rectangle contact unit is between 1:1.8and 1:1.2.
 9. The contact layout structure of claim 1, wherein an arearatio of the rectangle contact unit to the square contact unit isbetween 1:0.8 and 1:1.2.
 10. The contact layout structure of claim 1,wherein the second contact layouts respectively comprise a squarecontact unit.
 11. A contact structure comprising: a substrate having atleast a first region defined thereon; and plural sets of first contactspositioned along a predetermined direction in the first region, each setof the first contacts comprises: two first contact units; and twoadjacent second contact units positioned in between the two firstcontact units, and a connection line of center points of the secondcontact units being not overlapped to a connection line of center pointsof the first contact units.
 12. The contact structure of claim 11,wherein the first region comprises a dense region.
 13. The contactstructure of claim 12, wherein the first region comprises a staticrandom access memory (SRAM) region.
 14. The contact structure of claim11, wherein the predetermined direction is an X-axis direction or aY-axis direction.
 15. The contact structure of claim 11, wherein theconnection line of the center points of the two first contact units isparallel with the connection line of the center points of the two secondcontact units.
 16. The contact structure of claim 11, further comprisesa plurality of second contacts positioned in the first region, and anintegrity of the second contacts is smaller than an integrity of thefirst contacts.
 17. The contact structure of claim 16, whereinconnection lines of center points of the second contacts are overlappedto each other, and are parallel with the connection lines of the centerpoints of the first contact units and with the connection lines of thecenter points of the second contact units.
 18. The contact structure ofclaim 16, wherein the second contacts comprise a circle shape.
 19. Thecontact structure of claim 11, wherein the second contact units comprisean ellipsoidal shape.
 20. The contact structure of claim 19, wherein theellipsoidal shape comprises a long diameter and a short diameter.